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			<h1>Java 数组</h1>
<p>
数组对于每一门编程语言来说都是重要的数据结构之一，当然不同语言对数组的实现及处理也不尽相同。
</p>
<p>Java 语言中提供的数组是用来存储固定大小的同类型元素。</p>
<p>你可以声明一个数组变量，如 numbers[100] 来代替直接声明 100 个独立变量 number0，number1，....，number99。
</p>
<p>本教程将为大家介绍 Java 数组的声明、创建和初始化，并给出其对应的代码。</p>
<hr>
<h2>声明数组变量</h2>
<p>首先必须声明数组变量，才能在程序中使用数组。下面是声明数组变量的语法：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">dataType</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">arrayRefVar</span><span class="hl-code">;   </span><span class="hl-comment">//</span><span class="hl-comment"> 首选的方法</span><span class="hl-comment"></span><span class="hl-code">
 
或
 
</span><span class="hl-identifier">dataType</span><span class="hl-code"> </span><span class="hl-identifier">arrayRefVar</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code">;  </span><span class="hl-comment">//</span><span class="hl-comment"> 效果相同，但不是首选方法</span><span class="hl-comment"></span></div>
</div>
</div>
<p><strong>
注意:</strong> 建议使用 <strong>dataType[] arrayRefVar</strong> 的声明风格声明数组变量。
dataType arrayRefVar[] 风格是来自 C/C++ 语言 ，在Java中采用是为了让 C/C++ 程序员能够快速理解java语言。
</p>
<h3>实例</h3>
<p>下面是这两种语法的代码示例：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-types">double</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">myList</span><span class="hl-code">;         </span><span class="hl-comment">//</span><span class="hl-comment"> 首选的方法</span><span class="hl-comment"></span><span class="hl-code">
 
或
 
</span><span class="hl-types">double</span><span class="hl-code"> </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code">;         </span><span class="hl-comment">//</span><span class="hl-comment">  效果相同，但不是首选方法</span><span class="hl-comment"></span></div>
</div>
</div><hr>
<h2>创建数组</h2>
<p>Java语言使用new操作符来创建数组，语法如下：</p>
<pre>
arrayRefVar = new dataType[arraySize];
</pre>
<p>上面的语法语句做了两件事：</p>
<ul><li>
一、使用 dataType[arraySize] 创建了一个数组。</li>
<li>二、把新创建的数组的引用赋值给变量 arrayRefVar。</li></ul>
<p>数组变量的声明，和创建数组可以用一条语句完成，如下所示：</p>
<pre>
dataType[] arrayRefVar = new dataType[arraySize];
</pre>
<p>另外，你还可以使用如下的方式创建数组。</p>
<pre>
dataType[] arrayRefVar = {value0, value1, ..., valuek};
</pre>
<p>数组的元素是通过索引访问的。数组索引从 0 开始，所以索引值从 0 到 arrayRefVar.length-1。</p>
<h3>实例</h3>
<p>
下面的语句首先声明了一个数组变量 myList，接着创建了一个包含 10 个 double 类型元素的数组，并且把它的引用赋值给 myList 变量。
</p>
<div class="example">
<h2 class="example">TestArray.java 文件代码：</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-reserved">class</span><span class="hl-code"> </span><span class="hl-identifier">TestArray</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-types">static</span><span class="hl-code"> </span><span class="hl-types">void</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-brackets">(</span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">args</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
      </span><span class="hl-comment">//</span><span class="hl-comment"> 数组大小</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">size</span><span class="hl-code"> = </span><span class="hl-number">10</span><span class="hl-code">;
      </span><span class="hl-comment">//</span><span class="hl-comment"> 定义数组</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">myList</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-types">double</span><span class="hl-brackets">[</span><span class="hl-identifier">size</span><span class="hl-brackets">]</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">5</span><span class="hl-number">.6</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">4</span><span class="hl-number">.5</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">3</span><span class="hl-number">.3</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">13</span><span class="hl-number">.2</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">4</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">4</span><span class="hl-number">.0</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">5</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">34</span><span class="hl-number">.33</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">6</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">34</span><span class="hl-number">.0</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">7</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">45</span><span class="hl-number">.45</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">8</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">99</span><span class="hl-number">.993</span><span class="hl-code">;
      </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">9</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-number">11123</span><span class="hl-code">;
      </span><span class="hl-comment">//</span><span class="hl-comment"> 计算所有元素的总和</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-code"> </span><span class="hl-identifier">total</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">;
      </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">size</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
         </span><span class="hl-identifier">total</span><span class="hl-code"> += </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code">;
      </span><span class="hl-brackets">}</span><span class="hl-code">
      </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">println</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">总和为： </span><span class="hl-quotes">&quot;</span><span class="hl-code"> + </span><span class="hl-identifier">total</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-brackets">}</span><span class="hl-code">
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>以上实例输出结果为：</p>
<pre>
总和为： 11367.373
</pre>
<p>下面的图片描绘了数组 myList。这里 myList 数组里有 10 个 double 元素，它的下标从 0 到 9。</p>
<p><img decoding="async" src="//www.runoob.com/wp-content/uploads/2013/12/12-130Q0221Q5602.jpg" alt="java数组结构说明" /></p><hr>
<h2>处理数组</h2>
<p>数组的元素类型和数组的大小都是确定的，所以当处理数组元素时候，我们通常使用基本循环或者 For-Each 循环。</p>
<h3>示例</h3>
<p>
该实例完整地展示了如何创建、初始化和操纵数组：</p>
<div class="example">
<h2 class="example">TestArray.java 文件代码：</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-reserved">class</span><span class="hl-code"> </span><span class="hl-identifier">TestArray</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-types">static</span><span class="hl-code"> </span><span class="hl-types">void</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-brackets">(</span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">args</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">myList</span><span class="hl-code"> = </span><span class="hl-brackets">{</span><span class="hl-number">1</span><span class="hl-number">.9</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-number">.9</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-number">.4</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-number">.5</span><span class="hl-brackets">}</span><span class="hl-code">;
 
      </span><span class="hl-comment">//</span><span class="hl-comment"> 打印所有数组元素</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">myList</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
         </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">println</span><span class="hl-brackets">(</span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code"> + </span><span class="hl-quotes">&quot;</span><span class="hl-string"> </span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
      </span><span class="hl-brackets">}</span><span class="hl-code">
      </span><span class="hl-comment">//</span><span class="hl-comment"> 计算所有元素的总和</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-code"> </span><span class="hl-identifier">total</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">;
      </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">myList</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
         </span><span class="hl-identifier">total</span><span class="hl-code"> += </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code">;
      </span><span class="hl-brackets">}</span><span class="hl-code">
      </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">println</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">Total is </span><span class="hl-quotes">&quot;</span><span class="hl-code"> + </span><span class="hl-identifier">total</span><span class="hl-brackets">)</span><span class="hl-code">;
      </span><span class="hl-comment">//</span><span class="hl-comment"> 查找最大元素</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-code"> </span><span class="hl-identifier">max</span><span class="hl-code"> = </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code">;
      </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">1</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">myList</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
         </span><span class="hl-reserved">if</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code"> &gt; </span><span class="hl-identifier">max</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-identifier">max</span><span class="hl-code"> = </span><span class="hl-identifier">myList</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code">;
      </span><span class="hl-brackets">}</span><span class="hl-code">
      </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">println</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">Max is </span><span class="hl-quotes">&quot;</span><span class="hl-code"> + </span><span class="hl-identifier">max</span><span class="hl-brackets">)</span><span class="hl-code">;
   </span><span class="hl-brackets">}</span><span class="hl-code">
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>以上实例编译运行结果如下：</p>
<pre>
1.9
2.9
3.4
3.5
Total is 11.7
Max is 3.5
</pre>
<hr>
<h2>For-Each 循环</h2>
<p>JDK 1.5 引进了一种新的循环类型，被称为 For-Each 循环或者加强型循环，它能在不使用下标的情况下遍历数组。</p>
<p>语法格式如下：</p>
<pre>for(type element: array)
{
    System.out.println(element);
}</pre>
<h3>
实例</h3><p>
该实例用来显示数组 myList 中的所有元素：</p>

<div class="example">
<h2 class="example">TestArray.java 文件代码：</h2> 
<div class="example_code">
<div class="hl-main"><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-reserved">class</span><span class="hl-code"> </span><span class="hl-identifier">TestArray</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
   </span><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-types">static</span><span class="hl-code"> </span><span class="hl-types">void</span><span class="hl-code"> </span><span class="hl-identifier">main</span><span class="hl-brackets">(</span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">args</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
      </span><span class="hl-types">double</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">myList</span><span class="hl-code"> = </span><span class="hl-brackets">{</span><span class="hl-number">1</span><span class="hl-number">.9</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-number">.9</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-number">.4</span><span class="hl-code">, </span><span class="hl-number">3</span><span class="hl-number">.5</span><span class="hl-brackets">}</span><span class="hl-code">;
 
      </span><span class="hl-comment">//</span><span class="hl-comment"> 打印所有数组元素</span><span class="hl-comment"></span><span class="hl-code">
      </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">double</span><span class="hl-code"> </span><span class="hl-identifier">element</span><span class="hl-code">: </span><span class="hl-identifier">myList</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
         </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">println</span><span class="hl-brackets">(</span><span class="hl-identifier">element</span><span class="hl-brackets">)</span><span class="hl-code">;
      </span><span class="hl-brackets">}</span><span class="hl-code">
   </span><span class="hl-brackets">}</span><span class="hl-code">
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>以上实例编译运行结果如下：</p>
<pre>
1.9
2.9
3.4
3.5
</pre><hr>
<h2>数组作为函数的参数</h2>
<p>数组可以作为参数传递给方法。</p><p>例如，下面的例子就是一个打印 int 数组中元素的方法:</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-types">static</span><span class="hl-code"> </span><span class="hl-types">void</span><span class="hl-code"> </span><span class="hl-identifier">printArray</span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">array</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
  </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">array</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
    </span><span class="hl-identifier">System</span><span class="hl-code">.</span><span class="hl-identifier">out</span><span class="hl-code">.</span><span class="hl-identifier">print</span><span class="hl-brackets">(</span><span class="hl-identifier">array</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code"> + </span><span class="hl-quotes">&quot;</span><span class="hl-string"> </span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
  </span><span class="hl-brackets">}</span><span class="hl-code">
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>下面例子调用 printArray 方法打印出 3，1，2，6，4 和 2：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">printArray</span><span class="hl-brackets">(</span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-brackets">{</span><span class="hl-number">3</span><span class="hl-code">, </span><span class="hl-number">1</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-code">, </span><span class="hl-number">6</span><span class="hl-code">, </span><span class="hl-number">4</span><span class="hl-code">, </span><span class="hl-number">2</span><span class="hl-brackets">}</span><span class="hl-brackets">)</span><span class="hl-code">;</span></div>
</div>
</div><hr>
<h2>数组作为函数的返回值</h2>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-reserved">public</span><span class="hl-code"> </span><span class="hl-types">static</span><span class="hl-code"> </span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">reverse</span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">list</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
  </span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">result</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-identifier">list</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-brackets">]</span><span class="hl-code">;
 
  </span><span class="hl-reserved">for</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-types">int</span><span class="hl-code"> </span><span class="hl-identifier">i</span><span class="hl-code"> = </span><span class="hl-number">0</span><span class="hl-code">, </span><span class="hl-identifier">j</span><span class="hl-code"> = </span><span class="hl-identifier">result</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code"> - </span><span class="hl-number">1</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code"> &lt; </span><span class="hl-identifier">list</span><span class="hl-code">.</span><span class="hl-identifier">length</span><span class="hl-code">; </span><span class="hl-identifier">i</span><span class="hl-code">++, </span><span class="hl-identifier">j</span><span class="hl-code">--</span><span class="hl-brackets">)</span><span class="hl-code"> </span><span class="hl-brackets">{</span><span class="hl-code">
    </span><span class="hl-identifier">result</span><span class="hl-brackets">[</span><span class="hl-identifier">j</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-identifier">list</span><span class="hl-brackets">[</span><span class="hl-identifier">i</span><span class="hl-brackets">]</span><span class="hl-code">;
  </span><span class="hl-brackets">}</span><span class="hl-code">
  </span><span class="hl-reserved">return</span><span class="hl-code"> </span><span class="hl-identifier">result</span><span class="hl-code">;
</span><span class="hl-brackets">}</span></div>
</div>
</div>
<p>以上实例中 result 数组作为函数的返回值。</p>

<hr>
<h2>多维数组</h2>
<p>多维数组可以看成是数组的数组，比如二维数组就是一个特殊的一维数组，其每一个元素都是一个一维数组，例如：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">str</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">4</span><span class="hl-brackets">]</span><span class="hl-code">;</span></div>
</div>
</div>
<h3>多维数组的动态初始化（以二维数组为例）</h3>

<p>1. 直接为每一维分配空间，格式如下： </p> 
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">type</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">typeName</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">type</span><span class="hl-brackets">[</span><span class="hl-identifier">typeLength1</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-identifier">typeLength2</span><span class="hl-brackets">]</span><span class="hl-code">;</span></div>
</div>
</div>
<p>type 可以为基本数据类型和复合数据类型，typeLength1 和 typeLength2 必须为正整数，typeLength1 为行数，typeLength2 为列数。</p>
<p>例如：</p>  
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">a</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-types">int</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-code">;</span></div>
</div>
</div>
<p>解析：</p>
<p>二维数组 a 可以看成一个两行三列的数组。</p>
<p>2. 从最高维开始，分别为每一维分配空间，例如：  
</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code"> </span><span class="hl-identifier">s</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-brackets">]</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">[</span><span class="hl-number">3</span><span class="hl-brackets">]</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">Good</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">Luck</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">to</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">you</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;
</span><span class="hl-identifier">s</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">2</span><span class="hl-brackets">]</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">String</span><span class="hl-brackets">(</span><span class="hl-quotes">&quot;</span><span class="hl-string">!</span><span class="hl-quotes">&quot;</span><span class="hl-brackets">)</span><span class="hl-code">;</span></div>
</div>
</div>
<p>解析：  
</p><p>
<strong>s[0]=new String[2]</strong> 和 <strong>s[1]=new String[3]</strong> 是为最高维分配引用空间，也就是为最高维限制其能保存数据的最长的长度，然后再为其每个数组元素单独分配空间 <strong>s0=new String("Good")</strong> 等操作。
</p>
<h3>多维数组的引用（以二维数组为例）</h3>
<p>对二维数组中的每个元素，引用方式为 <strong>arrayName[index1][index2]</strong>，例如：</p>
<div class="example">
<div class="example_code">
<div class="hl-main"><span class="hl-identifier">num</span><span class="hl-brackets">[</span><span class="hl-number">1</span><span class="hl-brackets">]</span><span class="hl-brackets">[</span><span class="hl-number">0</span><span class="hl-brackets">]</span><span class="hl-code">;</span></div>
</div>
</div>
<hr>
<h2>Arrays 类</h2>
<p>
java.util.Arrays 类能方便地操作数组，它提供的所有方法都是静态的。</p><p>具有以下功能：</p>
<ul>
<li>给数组赋值：通过 fill 方法。</li>
<li>对数组排序：通过 sort 方法,按升序。</li>
<li>比较数组：通过 equals 方法比较数组中元素值是否相等。</li>
<li>查找数组元素：通过 binarySearch 方法能对排序好的数组进行二分查找法操作。</li>
</ul>
<p>具体说明请查看下表：</p>
<table class="reference">
	<tbody>
		<tr>
			<th style="width:76px;">
				序号</th>
			<th style="width:501px;">
				方法和说明</th>
		</tr>
		<tr>
			<td style="width:76px;">
				1</td>
			<td style="width:501px;">
				<strong>public static int binarySearch(Object[] a, Object key)</strong><br>
				用二分查找算法在给定数组中搜索给定值的对象(Byte,Int,double等)。数组在调用前必须排序好的。如果查找值包含在数组中，则返回搜索键的索引；否则返回 (-(<em>插入点</em>) - 1)。</td>
		</tr>
		<tr>
			<td style="width:76px;">
				2</td>
			<td style="width:501px;">
				<strong>public static boolean equals(long[] a, long[] a2)</strong><br>
				如果两个指定的 long 型数组彼此<em>相等</em>，则返回 true。如果两个数组包含相同数量的元素，并且两个数组中的所有相应元素对都是相等的，则认为这两个数组是相等的。换句话说，如果两个数组以相同顺序包含相同的元素，则两个数组是相等的。同样的方法适用于所有的其他基本数据类型（Byte，short，Int等）。</td>
		</tr>
		<tr>
			<td style="width:76px;">
				3</td>
			<td style="width:501px;">
				<strong>public static void fill(int[] a, int val)</strong><br>
				将指定的 int 值分配给指定 int 型数组指定范围中的每个元素。同样的方法适用于所有的其他基本数据类型（Byte，short，Int等）。</td>
		</tr>
		<tr>
			<td style="width:76px;">
				4</td>
			<td style="width:501px;">
				<strong>public static void sort(Object[] a)</strong><br>
				对指定对象数组根据其元素的自然顺序进行升序排列。同样的方法适用于所有的其他基本数据类型（Byte，short，Int等）。</td>
		</tr>
	</tbody>
</table>



<blockquote><h3>练习</h3>
<p><a href="https://c.runoob.com/quiz/5571" rel="noopener noreferrer" target="_blank">Java 数组测验</a></p></blockquote>

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<div id="postcomments"  style="display:none;" >
	<ol class="commentlist">
		<li class="comment even thread-even depth-1" id="comment-10674"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Jabin</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;957***846@qq.com</p></div><div id="runoobvote-id-10674" data-commid = "10674" class="upvotejs"><a class="upvote"></a> <span class="count">110</span></div></div><div class="comt-main" id="div-comment-10674"><p>数组倒序实例：</p>
<pre>
public class Test2 {
    public static void main(String[] args){
        int[] test= {1,2,4,5,7};
        for (int i : test) {
            System.out.print(i+" ");
        }
        System.out.println("\n");
        test = Test2.reverse(test);
        for (int i : test) {
            System.out.print(i+" ");
        }
    }

    public static int[] reverse(int[] arr){
        int[] result = new int[arr.length];
        for (int i = 0,j=result.length-1; i &lt; arr.length; i++,j--) {
            result[j] = arr[i];
        }
        return result;
    }
}
</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Jabin</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Jabin</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;957***846@qq.com</p></div></span>6年前 (2017-04-03)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-11076"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;飞翔的蒲公英</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;dar***o@163.com</p></div><div id="runoobvote-id-11076" data-commid = "11076" class="upvotejs"><a class="upvote"></a> <span class="count">63</span></div></div><div class="comt-main" id="div-comment-11076"><pre>
// 声明二维数组：有两行，列数待定，数组结构 = { { }, { } }

String s[][] = new String[2][]; 

// 确定每行的元素个数，第一行有2个元素，第二行有3个元素，

// 数组结构 = {{"E1", "E2"}, {"E1", "E2", "E3"}}

s[0] = new String[2];

s[1] = new String[3];
</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">飞翔的蒲公英</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;飞翔的蒲公英</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;dar***o@163.com</p></div></span>6年前 (2017-04-15)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-17442"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;angelra</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;264***8638@qq.com</p></div><div id="runoobvote-id-17442" data-commid = "17442" class="upvotejs"><a class="upvote"></a> <span class="count">36</span></div></div><div class="comt-main" id="div-comment-17442"><p>实现数组和字符串的转换处理</p>
<pre>public class Test {
    public static void main(String args[]) {
        String str = "helloworld";
        char[] data = str.toCharArray();// 将字符串转为数组
        for (int x = 0; x &lt; data.length; x++) {
            System.out.print(data[x] + "  ");
            data[x] -= 32;
            System.out.print(data[x] + "  ");
        }
        System.out.println(new String(data));
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">angelra</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;angelra</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;264***8638@qq.com</p></div></span>6年前 (2017-09-12)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-19924"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Hantn</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;473***567@qq.com</p></div><div id="runoobvote-id-19924" data-commid = "19924" class="upvotejs"><a class="upvote"></a> <span class="count">45</span></div></div><div class="comt-main" id="div-comment-19924"><p>冒泡排序</p>

<pre>public class BubbleSort {
/**
 * N个数字要排序完成，总共进行N-1趟排序，每i趟的排序次数为(N-i)次，所以可以用双重循环语句，外层控制循环多少趟，内层控制每一趟的循环次数。
 * @param args
 */
    public static void main(String[] args) {
        int arr[] = {26,15,29,66,99,88,36,77,111,1,6,8,8};
        for(int i=0;i &lt; arr.length-1;i++) {//外层循环控制排序趟数
            for(int j=0; j&lt; arr.length-i-1;j++) {
                        //内层循环控制每一趟排序多少次
                // 把小的值交换到前面
                if (arr[j]&gt;arr[j+1]) {
                    int temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
                }
            }
            System.out.print("第"+(i+1)+"次排序结果：");
                                //列举每次排序的数据
            for(int a=0;a&lt;arr.length;a++) {
                System.out.print(arr[a] + "\t");
            }
            System.out.println("");
        }
        System.out.println("最终排序结果：");
        for(int a = 0; a &lt; arr.length;a++) {
            System.out.println(arr[a] + "\t");
        }
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Hantn</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Hantn</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;473***567@qq.com</p></div></span>6年前 (2017-11-06)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-22503"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;WaterHole</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;710***626@qq.com</p></div><div id="runoobvote-id-22503" data-commid = "22503" class="upvotejs"><a class="upvote"></a> <span class="count">39</span></div></div><div class="comt-main" id="div-comment-22503"><p>选择排序：（比冒泡排序更快，运行次数更少）：</p>

<pre>public class Start
{
    public static void main(String[] args)
    {
        int[] arr={20,60,51,81,285,12,165,51,81,318,186,9,70};
        for(int a:arr)
        {
            System.out.print(a+" ");
        }
        
        System.out.println("\n"+"---------------从小到大---------------");
        
        arr=toSmall(arr);
        for(int a:arr)
        {
            System.out.print(a+" ");
        }
        
        System.out.println("\n"+"---------------从大到小---------------");
        
        arr=toBig(arr);
        for(int a:arr)
        {
            System.out.print(a+" ");
        }
    }
//    从大到小
    public static int[] toSmall(int[] arr)
    {
//遍历数组里除最后一个的其他所有数，因为最后的对象没有与之可以相比较的数
        for(int i=0;i&lt;arr.length-1;i++)
        {
/*遍历数组里没有排序的所有数，并与上一个数进行比较
 *&ldquo;k=i+1&rdquo;因为自身一定等于自身，所以相比没有意义
 *而前面已经排好序的数，在比较也没有意义
 */
            for(int k=i+1;k&lt;arr.length;k++)
            {
                if(arr[k]&lt;arr[i])//交换条件（排序条件）
                {
                    int number=arr[i];
                    arr[i]=arr[k];
                    arr[k]=number;
                }//交换
            }
        }
        return arr;
    }
//    从小到大
//和前面一样
    public static int[] toBig(int[] arr)
    {
        for(int i=0;i&lt;arr.length-1;i++)
        {
            for(int k=i+1;k&lt;arr.length;k++)
            {
                if(arr[k]&gt;arr[i])
                {
                    int number=arr[i];
                    arr[i]=arr[k];
                    arr[k]=number;
                }
            }
        }
        return arr;
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">WaterHole</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;WaterHole</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;710***626@qq.com</p></div></span>5年前 (2018-01-03)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-22610"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;冰糕</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;257***9843@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://blog.csdn.net/object_allen/article/details/41695425">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-22610" data-commid = "22610" class="upvotejs"><a class="upvote"></a> <span class="count">43</span></div></div><div class="comt-main" id="div-comment-22610"><p>java.util.Arrays类能方便地操作数组，它提供的所有方法都是静态的。具有以下功能：</p>
<ul><li>
给数组赋值：通过fill方法。</li><li>
对数组排序：通过sort方法,按升序。</li><li>
比较数组：通过equals方法比较数组中元素值是否相等。</li><li>
查找数组元素：通过binarySearch方法能对排序好的数组进行二分查找法操作。</li></ul>


<pre>import java.util.Arrays;

public class TestArrays {
    public static void output(int[] array) {
        if (array != null) {
            for (int i = 0; i &lt; array.length; i++) {
                System.out.print(array[i] + " ");
            }
        }
        System.out.println();
    }

    public static void main(String[] args) {
        int[] array = new int[5];
        // 填充数组
        Arrays.fill(array, 5);
        System.out.println("填充数组：Arrays.fill(array, 5)：");
        TestArrays.output(array);
        // 将数组的第2和第3个元素赋值为8
        Arrays.fill(array, 2, 4, 8);
        System.out.println("将数组的第2和第3个元素赋值为8：Arrays.fill(array, 2, 4, 8)：");
        TestArrays.output(array);
        int[] array1 = { 7, 8, 3, 2, 12, 6, 3, 5, 4 };
        // 对数组的第2个到第6个进行排序进行排序
        Arrays.sort(array1, 2, 7);
        System.out.println("对数组的第2个到第6个元素进行排序进行排序：Arrays.sort(array,2,7)：");
        TestArrays.output(array1);
        // 对整个数组进行排序
        Arrays.sort(array1);
        System.out.println("对整个数组进行排序：Arrays.sort(array1)：");
        TestArrays.output(array1);
        // 比较数组元素是否相等
        System.out.println("比较数组元素是否相等:Arrays.equals(array, array1):" + "\n" + Arrays.equals(array, array1));
        int[] array2 = array1.clone();
        System.out.println("克隆后数组元素是否相等:Arrays.equals(array1, array2):" + "\n" + Arrays.equals(array1, array2));
        // 使用二分搜索算法查找指定元素所在的下标（必须是排序好的，否则结果不正确）
        Arrays.sort(array1);
        System.out.println("元素3在array1中的位置：Arrays.binarySearch(array1, 3)：" + "\n" + Arrays.binarySearch(array1, 3));
        // 如果不存在就返回负数
        System.out.println("元素9在array1中的位置：Arrays.binarySearch(array1, 9)：" + "\n" + Arrays.binarySearch(array1, 9));
    }
}</pre>
 

<p>输出结果：</p>

<pre>填充数组：Arrays.fill(array, 5)：
5 5 5 5 5 
将数组的第2和第3个元素赋值为8：Arrays.fill(array, 2, 4, 8)：
5 5 8 8 5 
对数组的第2个到第6个元素进行排序进行排序：Arrays.sort(array,2,7)：
7 8 2 3 3 6 12 5 4 
对整个数组进行排序：Arrays.sort(array1)：
2 3 3 4 5 6 7 8 12 
比较数组元素是否相等:Arrays.equals(array, array1):
false
克隆后数组元素是否相等:Arrays.equals(array1, array2):
true
元素3在array1中的位置：Arrays.binarySearch(array1, 3)：
1
元素9在array1中的位置：Arrays.binarySearch(array1, 9)：
-9</pre>
<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">冰糕</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;冰糕</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;257***9843@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://blog.csdn.net/object_allen/article/details/41695425">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-01-04)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-25296"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;支上上</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;849***107@qq.com</p></div><div id="runoobvote-id-25296" data-commid = "25296" class="upvotejs"><a class="upvote"></a> <span class="count">36</span></div></div><div class="comt-main" id="div-comment-25296"><p>数组容量如果不够用可以使用 Arrays.copyOf() 进行扩容：</p>

<pre>Array.copy(E[] e,newLength);</pre>

<p>其第一个形参指的是需要扩容的数组，后面是扩容后的大小，其内部实现其实是使用了 System.arrayCopy(); 在内部重新创建一个长度为 newLength 类型是 E 的数组。</p>

<pre>import java.util.Arrays;  
public class Main {
    public static void main(String[] args) {
        int[] a= {10,20,30,40,50};
        a= Arrays.copyOf(a,a.length+1);
        for(int i=0;i&lt;a.length;i++) {
            System.out.println(a[i]);
        }
    }
}</pre>
<p>默认补 <strong>0</strong>，输出结果为： <span class="marked">10 20 30 40 50 0</span></p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">支上上</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;支上上</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;849***107@qq.com</p></div></span>5年前 (2018-03-20)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-25824"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;支上上</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;849***107@qq.com</p></div><div id="runoobvote-id-25824" data-commid = "25824" class="upvotejs"><a class="upvote"></a> <span class="count">17</span></div></div><div class="comt-main" id="div-comment-25824"><p data-title="Java 数组实现的一个小游戏"><strong>数组实现的一个小游戏</strong></p>
<p>程序随机产生5个按一定顺序排列的字符，作为猜测结果。</p>
<p>玩家可以猜测多次，每猜一次，若猜测的完全正确则游戏结束，并计算玩家的游戏得分并输出。若没有猜对，则提示猜测结果，如猜对了几个字符，以及猜对了几个字符的位置信息，并提示玩家游戏继续。若中途输入EXIT，则游戏提前结束</p>
<pre>import java.util.Scanner;

//猜字符小游戏
public class Guessing {
    private static Scanner scan;
    // 主方法
    public static void main(String[] args) {
        scan = new Scanner(System.in);
        char[] chs = generate();
        System.out.println(chs);
        int count = 0; // 猜错的次数
        while (true) { // 自造死循环
            System.out.println("猜吧!");
            String str = scan.next().toUpperCase(); // 获取用户输入的字符串
            if (str.equals("EXIT")) { // 判断字符串内容相等
                System.out.println("下次再来吧!");
                break;
            }
            char[] input = str.toCharArray(); // 将字符串转换为字符数组
            int[] result = check(chs, input);
            if (result[0] == chs.length) { // 对
                int score = 100 * chs.length - 10 * count;
                System.out.println("恭喜你，猜对了!得分为:" + score);
                break;
            } else {
                count++;
                System.out.println("字符对个数为:" + result[1] + "，位置对个数为:" + result[0]);
            }
        }
    }
    // 生成随机字符数组chs
    public static char[] generate() {
        char[] chs = new char[5];
        char[] letters = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
                'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
                'W', 'X', 'Y', 'Z' };
        boolean[] flags = new boolean[letters.length];
        for (int i = 0; i &lt; chs.length; i++) {
            int index;
            do {
                index = (int) (Math.random() * letters.length);
            } while (flags[index] == true);
            chs[i] = letters[index];
            flags[index] = true;
        }
        // i=0 index=0 chs[0]='A' flags[0]=true
        // i=1 index=25 chs[1]='Z' flags[25]=true
        // i=2 index=0/25/0/25/1 chs[2]='B' flags[1]=true
        return chs;
    }

    // 对比:随机字符数组chs与用户输入的字符数组input
    public static int[] check(char[] chs, char[] input) {
        int[] result = new int[2]; // (0,0)
        for (int i = 0; i &lt; chs.length; i++) {
            for (int j = 0; j &lt; input.length; j++) {
                if (chs[i] == input[j]) {
                    result[1]++;
                    if (i == j) {
                        result[0]++;
                    }
                    break;
                }
            }
        }
        return result;
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="../note/25824">支上上</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;支上上</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;849***107@qq.com</p></div></span>5年前 (2018-04-02)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-26438"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;tfbyly</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;905***717@qq.com</p></div><div id="runoobvote-id-26438" data-commid = "26438" class="upvotejs"><a class="upvote"></a> <span class="count">15</span></div></div><div class="comt-main" id="div-comment-26438"><p>数组这里有一个问题容易搞不清楚的。</p>

<p>在 java 中，关于数组描述正确的是(  <strong>B，D </strong> ) </p>
<ul><li>
A.数组中的索引下标从1开始
</li><li>
B.存储在数组当中的数据都属于同一数据类型
</li><li>
C.通过数组名.length()能获得数组的长度
</li><li>
D.数组的最大索引下标是数组的长度减1
</li></ul>
<p>比如说一个 int 类型的数组: </p>


<pre>int[] arr = { 'a', 25, 45, 78, 'z' };
System.out.println(Arrays.toString(arr));</pre>


<p>输出结果是：<span class="marked">[97, 25, 45, 78, 122]</span></p>

<p>存放进去的 char 类型的字符会自动转为 int 类型的 ASCII 码。</p>

<p>上面的代码中就将 a 转成了 97，z 转成了 122。</p>

<p>所以数组只能存放同一类型的数据是正确的。</p>

<p><strong>D选项。</strong></p>

<p>数组的长度固定时，为了防止下标越界，应该在索引的时候将下标减一。</p>


<pre>int[] arr = { 'a', 25, 45, 78, 'z' };
int arrs = arr[5];
System.out.println(Arrays.toString(arr));
System.out.println(arrs);</pre>


<p>上面的代码中数组总长度为 5，因为数组是索引是从 0 开始取值，索引取值为5的时候就会产生下标越界异常，在这里最大的索引应当为 4。</p>

<pre>Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">tfbyly</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;tfbyly</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;905***717@qq.com</p></div></span>5年前 (2018-04-18)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-44779"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;路过顺便打酱油</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;782***197@qq.com</p></div><div id="runoobvote-id-44779" data-commid = "44779" class="upvotejs"><a class="upvote"></a> <span class="count">17</span></div></div><div class="comt-main" id="div-comment-44779"><p>对于上面的冒泡排序，其实没必要那么复杂，最终得到的是结果，我们只需要理解冒泡排序要排多少次就可以了。比如 1-9 比较，1-2,2-3 等，需要 9 次出一个最大最小数，然后再次去比较出第二个数字，所有自然想到了嵌套循环；代码如下：</p>

<pre>//冒泡
int[] num={2,4,9,1,6,7,9,12,63,4,87,54,67,65,4};
int totle;
for(int i=0;i&lt;num.length;i++){
    for(int j=0;j&lt;i;j++){
        if(num[j]&gt;num[i]){
            totle=num[j];
            num[j]=num[i];
            num[i]=totle;
        }
    }
}

for(int i=num.length-1;0&lt;=i;i--){
    for(int j=i;0&lt;=j;j--){
        if(num[j]&gt;num[i]){
            totle=num[j];
            num[j]=num[i];
            num[i]=totle;
        }
    }
}
for (int k : num) {
    System.out.print(k+"===");
}</pre>

<p>两次循环代码都可以出结果，区别在于一个是累加，一个是累减，随便去掉一个循环代码还是能得到结果</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">路过顺便打酱油</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;路过顺便打酱油</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;782***197@qq.com</p></div></span>4年前 (2019-07-18)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-56102"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;好劲的维</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;pal***@qq.com</p></div><div id="runoobvote-id-56102" data-commid = "56102" class="upvotejs"><a class="upvote"></a> <span class="count">21</span></div></div><div class="comt-main" id="div-comment-56102"><h3>Java.util.Arrays 类的排序拓展</h3>

<p>java.util.Arrays.sort 只可以用于按升序排列数组，若按降序排序可以使用 <span class="marked">Arrays.sort(数组,Collections.reverseOrder())</span>。</p>

<p>调用的其实 Arrays.sort 的静态方法之一 Arrays.sort(Integer[] a,Comparator cmp)。</p>
<p>
对于 Collections.reverseOrder() 官方解释：</p>
<p>
reverseOrder() 方法用于获取一个比较有否就实现 Comparable 接口的对象的集合的自然顺序相反。</p>
<pre>import java.util.Arrays;
import java.util.Collections;

public class Main {
    public static void main(String []args) {
        Double[] list_double = new Double[10];
        list_double[0] = 1.2;
        list_double[1] = 2.2;
        list_double[2] = 8.2;
        list_double[3] = 4.2;
        list_double[4] = 7.2;
        list_double[5] = 6.2;
        list_double[6] = 5.2;
        list_double[7] = 4.2;
        list_double[8] = 9.2;
        list_double[9] = 10.2;

        java.util.Arrays.sort(list_double);
        System.out.println("升序:");
        for(double emp:list_double)
        {
            System.out.println(emp);
        }
        
        Arrays.sort(list_double,Collections.reverseOrder());
        System.out.println("降序:");
        for(double emp:list_double)
        {
            System.out.println(emp);
        }
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">好劲的维</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;好劲的维</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;pal***@qq.com</p></div></span>3年前 (2020-08-10)</div></div></li><!-- #comment-## -->
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		noteContent = noteContent.replace(/<pre><code>/g,"<pre>");
		noteContent = noteContent.replace(/<\/code><\/pre>/g,"</pre>");
		
		// 系列化表单数据
		var comment_parent = 0;
		var is_user_logged_in = $("#is_user_logged_in").val();
		var comment_post_ID =  5005;
		var _wp_unfiltered_html_comment = $("#_wp_unfiltered_html_comment").val();
		var comment = noteContent;
		var author = $("#author").val();
		var url = $("#url").val();
		var email = $("#email").val();
		if(isBlank(author) && is_user_logged_in==0) {
			statusdiv.html('<p  class="ajax-error">请输入昵称！</p>').show();
		} else if(isBlank(email)  && is_user_logged_in==0) {
			statusdiv.html('<p  class="ajax-error">请输入邮箱！</p>').show();
		} else {
			// var formdata=commentform.serialize() + "&comment=" + noteContent ;
			// 添加状态信息
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			var formurl=commentform.attr('action');
			
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					url: formurl,
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					data: {"comment_parent":comment_parent,"comment_post_ID":comment_post_ID, "_wp_unfiltered_html_comment":_wp_unfiltered_html_comment,"comment":comment,"url":url, "email":email,"author":author},
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					}else{
						statusdiv.html('<p class="ajax-error" >'+data.msg+'</p>').show();
					}
					commentform.find('textarea[name=comment]').val('');
				}
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			setTimeout(function(){
		        $("#submit").prop('disabled', false);
		    }, 10*1000);
		}
		return false;

	});
	$(".comt-author").click(function() {
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			var ajax_data = {
				_vote_action: _vote_action,
				action: "pinglun_zan",
				um_id: um_id,
				um_action: "ding"
			};
			//console.log(ajax_data);
			$.post(ajaxurl,ajax_data,function(status){
				//if(status.vote_num>999) {
				//	_voteHtml = '<span style="display: block; text-align: center;font-size: 20px; color: #6a737c; margin: 8px 0;">'+kFormatter(status.vote_num) +'</span>';
				//	$("#runoobvote-id-" + um_id + " .count").hide().after(_voteHtml);
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			});
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	};
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		$.post(ajaxurl,{"action":"pinglun_zan","postid":5005},function(data){  
			$(data).each(function(key,value) {
				$("#runoobvote-id-" + value.commid + " .upvote").addClass(value.upvotejs_class);
				$("#runoobvote-id-" + value.commid + " .downvote").addClass(value.downvote_class);
				$("#runoobvote-id-" + value.commid + " .count").text(value.upvote_count);
			})
		},'json');
		
	}
	
	
});
function isBlank(str) {
    return (!str || /^\s*$/.test(str));
}
function kFormatter(num) {
	// return num;
    return Math.abs(num) > 999 ? Math.sign(num)*((Math.abs(num)/1000).toFixed(1)) + 'k' : Math.sign(num)*Math.abs(num)
}

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